Methods of Specialized Investigation

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Being burned alive is one of the most horrific ways to die. As a result, there are few crimes more horrific than arson. Unfortunately, detecting and apprehending an arsonist has proven to be one of the most challenging tasks for most investigators in many countries. Fire investigations are frequently difficult for a variety of reasons. For starters, determining whether a fire was intentionally set is often difficult. Arsonists also tend to destroy any evidence that could be used against them. As a result, it makes it much more difficult for investigators to get to the bottom of a fire event.  One real-world criminal case is that of the Multiple deaths if Clarence Roberts. Clarence Roberts was one of the most prominent people in Indiana. On November 1970, his garage was destroyed by a fierce fire and the body of a man at the scene was severely burned ("The fiery death of Clarence Roberts -- now or then?", 2017). The dead man was identified as Clarence but it later become complex. Clarence’s wife, Geneva, was to get a substantial life insurance payout in the event of the death of her husband. Lab analysis showed that the man was not Clarence as he had a different blood type. Although his ring was also found at the scene, it did not have any signs of damage or heat. It seemed to have been planted there. Geneva never received the life insurance policy payout and on November 1980, Geneva was killed by a fire in her home and was found next to a body suspected to be that of Clarence ("The fiery death of Clarence Roberts -- now or then?", 2017). However, speculation still remains as to the third party that started the fire which killed both Geneva and Clarence. The paper analyzes the investigative strategies that can be used in such a case as well as the techniques or resources that would be used to obtain leads. It also explores the fundamentals of investigation that would be used to identify the perpetrator and the strengths and limitations of the techniques used.

What investigative strategies will you put into play to solve this criminal offense?

Establishing the first responders’ role

When responding to a fire, the personnel would observe the conditions and activities that are taking place at and near the scene of crime (International Association of Fire Chiefs, International Association of Arson Investigators, & National Fire Protection Association, 2012). Valuable information can be gained when approaching and also on the arrival at the scene. As soon as conditions permit, the responders should be initiate documentation of the information (Bieber, 2014). The records they should document include presence, conditions of the witnesses and victims and also the location. Smoke and flame conditions, weather conditions, the use of the structure and type of occupancy and any unusual characteristics of the scene should be all be documented (International Association of Fire Chiefs, 2016).

Evaluate the Scene

The first step an investigator needs to take in introduce himself/herself as well the role to be undertaken. A preliminary scene assessment should then be conducted to protect evidence and also to provide safety. The investigator should then determine the area where investigations will be focused and adjust the perimeter of the scene accordingly (Bieber, 2014). Witnesses at the scene of accident should then be identified and interviewed. Once the names of the witnesses have been obtained and interviews arranged, the scene security at the time of the incident should be evaluated (International Association of Fire Chiefs, 2016). The investigator should check whether the building had been secured, whether suppression and fire detection systems were operational at the time of the fire.

Documentation of the scene

Documentation is majorly done by photographing or videotaping the scene. Photographic documentation provides a visual image of the scene and also supplements the written records and witness statements (International Association of Fire Chiefs, International Association of Arson Investigators, & National Fire Protection Association, 2012). As the investigation is undertaken, videography and photography should also occur to preserve and create a visual record (Bieber, 2014). Once the visual images of the scene have been obtained, an investigator should then describe and document the scene. Written descriptions, narratives and observations of the possible causes of fire are then documented. An accurate sketch of the scene is also prepared to give more insight into the outlook of the scene of fire.

Processing Evidence

The first step towards the processing of evidence is the identification and collection of evidence. Evidence collection at the scene of arson requires that investigators are attentive to documentation and maintaining their integrity (International Association of Fire Chiefs, 2016). Evidence should be identified and properly documented for laboratory analyses, court proceeding and even further investigations. Prevention of evidence contamination is an area that requires special attention (International Association of Fire Chiefs, International Association of Arson Investigators, & National Fire Protection Association, 2012). Access to the scene of fire should be controlled and the evidence collected should be stored and transported in a manner that avoids contamination (Bieber, 2014). The investigator should also ensure packaging procedure, transportation and storage procedure id adhered to in order preserve the conditions of the samples. A chain of custody should then be established and maintained. It ensures that the integrity of the evidence is verified. Written records documenting the description of the evidence, the sample number, the location and date where found as well as the collector’s name should be maintained (International Association of Fire Chiefs, 2016). All transfers of custody as well as the names of the recipient also have to be documented.

Completion of the scene investigation

The investigator should ensure that reasonable efforts to identify, collect and remove all evidence from the scene have been done before releasing it. Also, safety, health and legal issues must be articulated to the person in charge of receiving the scene and public safety agencies should be aware of any such moves (Bieber, 2014). Doing such due diligence minimizes the risk of future injury and accidents as well as potential liability in case a person is injured or a property destroyed. Reports should then be submitted to the appropriate database. It involves the collection of detailed fire information, integration and dissemination through state and national databases. The records help authorities to determine trends in fire incidents, and develop innovative equipment and procedures to counter them.

Resources or techniques to obtain or follow leads in arson cases


The use of computers in arson investigations has gained pace just as in business and government. Computers have the capability of running different application programs for database management, communications, numerical analysis and graphics (International Association of Fire Chiefs, International Association of Arson Investigators, & National Fire Protection Association, 2012). The friendly nature of these programs have made them popular in fire investigation. As a result, investigators can use the computer programs to prepare fire scene diagrams, analyze fire statistics and financial information, maintain investigation records and write reports among others (Bieber, 2014). Computers can also be used to communicate with law enforcement and fire protection professionals through electronic information services. Other sophisticated compute fire models and programs such as the Fire Research Laboratory, the National institute for Standards and Technology can also be used by fire investigators to document and understand whatever they are investigating (International Association of Fire Chiefs, 2016).

Accelerant Detection

The determination whether a fire is incendiary can be tested in the presence of combustible or flammable liquid accelerants (Bieber, 2014). Accelerant detection hence is used to detect whether there is combustible or flammable liquid accelerants in fire debris. However, the success of this technique is dependent on an investigator’s senses of small, touch and sight.

Mechanical and Electronic Equipment

Electronic or mechanical devices for detecting accelerant vapors are divided into four categories. These include catalytic combustion detectors, flame ionization detectors, photo ionization detectors, semi-conductor based instruments (Pietzak, International Association of Arson Investigators, & National Fire Protection Association, 2013).

Catalytic Combustion Detectors

It consists of three important components. A pump for drawing a sample into the instrument, a gauge that indicates changes in coil resistance and a chamber that contains a platinum wire coil (International Association of Fire Chiefs, 2016). The detectors’ operation is based on the electro-mechanical principal that electrical resistance and heat are related. In the event that a sample of accelerant contaminated air/vapor mixture is forced into the chamber, the heat oxidizes the chamber and the temperature rises (Bieber, 2014). The increase in temperature in turn increases the coil’s resistance which is then registered on the gauge of the instrument.

Photo-ionization detectors

Photo-ionization detectors utilize the concept of high frequency sources of light in the far ultraviolet range in the production of ionization contaminants in air samples that enter the detector (Bieber, 2014). Ionization of hydrocarbon samples lead to the attraction of free electrons to a cathode. The change of current that results is then amplified and registered by a strip chart recorder. The devices often exhibit a good selection of hydrocarbons and are quite sensitive (Pietzak, International Association of Arson Investigators, & National Fire Protection Association, 2013).

Semiconductor Sensor Instruments

Semiconductor Sensor Instruments use a semiconductor chip that detects the presence of hydrocarbon vapors. High concentrations of hydrocarbons in the air infiltrate the crystalline structure in the chip and subsequently changes its conductive properties (Bieber, 2014). An analog reading on a meter is then produced once registered and amplified. Through calibration or comparison, the simple design together with a duplicate sensor allows for the elimination of background sources.

Flame ionization detectors

Flame ionization detectors function by mixing the sample air/vapor mixture with hydrogen then burning. The molecules of the mixture then ionize due to the high temperature that results from burning (International Association of Fire Chiefs, International Association of Arson Investigators, & National Fire Protection Association, 2012). Ionization in this case means the breakdown of molecules into electrically charged chemical species. The gas mixture then becomes electrically conductive. The extent of ionization is measured by an electrometer to produce readings that show the presence of accelerants.

Forensic Techniques

Forensic science has emerged as an important tool in the investigation of arson cases. It provides important tools in the documentation and verification of the field investigators findings (International Association of Fire Chiefs, 2016). Principles of physics and analytical chemistry are applied in the identification, classification and comparison of samples collected by investigators (Bieber, 2014). Forensic techniques involve specialized and complex equipment that require the professionalism and competence of field investigators working to obtain and analyze evidence.

Fire Investigation Vehicles

Fire investigation vehicles are important in transporting the different tools and equipment required in the scene of fire. Furthermore, the vehicles also serve as command posts to facilitate co-ordination of the investigation process (Bieber, 2014). Similar to other law enforcement vehicles, the ‘arson vans’ are often specialized. The van or the truck deployed to the scene of the investigation should have an enclosed cargo body. It should also be equipped with public address systems, emergency response equipment and radios. Unites of this type facilitates the transportation of an array of tools and equipment such as digging tools scene security supplies, and salvage tools (International Association of Fire Chiefs, 2016). The investigation team can also prefer a unit that is equipped with remote surveillance equipment, cellular phones, portable computers, forensic analysis equipment and facsimile machines.

Fundamentals of Investigations to identify a perpetrator

One of the major ways in which you can identify a perpetrator of arson and build a solid case is through the examination of trace evidence. Trace evidence includes different clues or materials other than accelerant samples that may indicate the identity of a suspect, the motive of the suspect and or within the cause and origin of the fire. Examples of trace evidence include

Questioned Documents: Documents such as insurance certificates and policies, letters, property records and titles, financial records, business papers or checks can be used to find clues into an arson investigation (International Association of Fire Chiefs, 2016). Why, how and when a document is prepared as well as the information contained may provide clues into who may be responsible for the fire and the motive behind the act of arson.

Serological samples: These include skin, DNA, hair or blood. Such evidence is often important in eliminating or identifying arson suspects (Bieber, 2014). However, DNA fingerprinting technology has developed over the years, making the process of identifying an arsonist quite easy.

Latent Fingerprints: Fingerprints are another important means of identifying arson suspects as well as positively identifying the victims of an arson (Pietzak, International Association of Arson Investigators, & National Fire Protection Association, 2013). Latent fingerprints are usually discovered on failed incendiary devices, and accelerant containers among others. Small fragments of the devices or containers used in an arson are may contain enough information for the positive identification of an arsonist.

Tool Marks: Tools used in cutting, lifting and prying in most cases leave a lot of distinctive marks. The tools can be used to identify the source of damage to cabinets, doors, windows and other secure locations (Pietzak, International Association of Arson Investigators, & National Fire Protection Association, 2013). In most cases, the evidence obtained from tools is often used to rule out the damage that was caused by firefighters when forced their entry into a burning premise (Bieber, 2014). In addition, the marks on bodies on victims can be identified in the same fashion. In addition, comparison of devices and tools can also be used to establish if a particular tool was used in damaging a premise.

Comparison Samples

Comparison samples are objects or materials that are believed to be nearly similar to accelerant debris samples but they do not contain accelerant residues. Such samples minimize, identify or eliminate sources of interference in the analysis of the samples. Comparison samples include:

Comparable Accelerant Samples: In most cases, investigators often have to identify similarities between samples obtained or found in other sources near the scene of fire and combustible and flammable liquid residues from known combustible and flammable liquids collected in the fire debris (Bieber, 2014). Combustible and flammable liquid residue samples may come from sources on the scene and may have been brought to the scene by another source (International Association of Fire Chiefs, International Association of Arson Investigators, & National Fire Protection Association, 2012). Comparing debris samples with samples of liquids from these sources together with comparison samples of materials that are similar to the ones present in the fire debris may be an important method in differentiating between what was at the scene and what was brought to the scene to start or spread the fire (International Association of Fire Chiefs, 2016).

Comparable Material Samples: It is important that samples of materials that are similar to those found in the accelerant debris matrix that are identical but do not have any accelerant are collected (Bieber, 2014). Examples of such materials include wood or carpet trim which gives out pyrolysis products that often obscure accelerant patterns during analysis. Hence, for every questioned fire debris, a comparison sample should be collected (International Association of Fire Chiefs, 2016). Comparison samples are important in making a positive identification if a material. In the event of a doubt about whether a comparison sample is required, it should immediately be collected and submitted or a lab should be contacted.

Strengths and Limitations of Arson Investigation Techniques


The use of modern techniques such as data analysis and accelerant detectors reduce bias.

Statistical control can be achieved through the use of different equipment

Communication vehicles co-ordinate commination between those at the scene of the fire

Common tools and equipment at the scene of fire can be used to access the building, excavate evidence to identify the origin of the fire

The use of forensic technique reduces chances of human error in the collection and interpretation of date


Gathering and Interpreting evidence is flawed

Despite the guidance provided by the NFPA 921 together with scientific advances, several issues are still holding back investigations of arson (Yao, et al, 2014). These problems have prevented fire investigation from being regarded as a true forensic discipline. When fire burns, great evidence is destroyed and damaged. DNA, fingerprints and trace evidence become unusable (International Association of Fire Chiefs, 2016). However, as the heat reduces, it creates a unique class of evidence that has over the years been used to determine cause and origin. Examination of evidence that has been created by fire creates a fire pattern that is often analyzed. Unfortunately, the fire dynamics or pattern does not determine a motive, identify a suspect or even establish if a crime occurred.

The longer the fire, the greater the chance of error

The process of determining the origin of a fire involves examining and interpreting the damage caused by the fire. If a fire is extinguished early, determining where it originated from can be quite a straightforward process (Yao, et al, 2014). However, if the fire is allowed to burn for long, the evidence created becomes complex, making the interpretation more difficult and subjective.

Lack of Enforceable Standard

Fire investigators often believe that it is a form of art and not science. As a result, the NFPA has never been fully embraced despite giving policies and procedures on how to conduct arson investigations (Yao, et al, 2014).


Fire investigations have proven to be one of the most difficult incidences to successfully investigate. Over the years, technology has been increasingly used in the field of arson investigation. However, not many are convicted for arson despite clear evidence that certain fires were caused by a person or a group of people. Techniques such as accelerant detection, computer programs and forensic techniques are all important resources and techniques that can be used in the investigation of an arson. To build a case against an arsonist, investigators today have to focus on certain trace evidence, such as latent fingerprints, latent fingerprints and serological samples. Also, comparable accelerant samples and comparable material samples have to be carefully scrutinized to provide a lead to finding the perpetrator of the crime.


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Bieber, P. (2014). Fire investigation and cognitive bias. Wiley Encyclopedia of Forensic Science.

International Association of Fire Chiefs. (2016). Fire investigator: Principles and practice to NFPA 921 & 1033.

International Association of Fire Chiefs., International Association of Arson Investigators., & National Fire Protection Association. (2012). Fire investigator: Principles and practice to NFPA 921 and 1033. Sudbury, MA: Jones & Bartlett Learning.

Pietzak, G., International Association of Arson Investigators., & National Fire Protection Association. (2013). Fire investigator field guide. Burlington, MA: Jones & Bartlett Learning.

The fiery death of Clarence Roberts -- now or then?. (2017). UPI. Retrieved 22 October 2017, from

Yao, H. W., Li, Y. Y., Shen, H., & Liang, D. (2014). Advances in Analytical Technologies of Trace Accelerant in Fire Investigation. In Intelligent Computation Technology and Automation (ICICTA), 2014 7th International Conference on (pp. 49-51). IEEE.

May 02, 2023

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